Why do I shake when I get horny?

I've noticed that nearly every time I start to get horny my body starts to shake. I used to get really nervous and I've learned to harness that a bit, but it does not stop the shaking. It's like a nervous shaking but I don't feel nervous, if that makes sense. My girlfriend asks me about it and I tell her I don't know why it happens. Does anyone else experience this?

It happens to me sometimes...when Im reeeeally horny and anticipating something happening. No idea why...it only happens sometimes and lasts a minute or so then I calm down and get on with things...maybe its excitement so adrenaline?

It happens to me any time I get nervous, excited, or anxious. Once I get past the initial stages of excitement, I calm down. That takes a few weeks of getting used to someone... or a few "times" if we're just get right to it.